Nickel Nanocatalyst Supported Single-Step Hydroconversion of Dicyclopentadiene (DCPD) into High Energy-Density Fuel, Exo-Tetrahydrodicyclopentadiene (Exo-THDCPD).

There are several chemical methods for the synthesis of high energy-density fuel, exotetrahydrodicyclopentadiene (exo-THDCPD), however, still there is a challenge to synthesize exo-THDCPD conveniently. In present work, the exo-THDCPD from dicyclopentadiene (DCPD) has successfully synthesized through simplest and greener single step hydroconversion reaction over mesoporous supported nickel nanocatalyst (Ni/MCM-41). The reaction performed in autoclave under a hydrogen pressure ranging from 300-400 (Psi), temperature range 130-150 °C and progress has been monitored by gas chromatography which reveals that the reaction mechanism goes through dissociation-recombination of DCPD. The major reaction parameters such as temperature, pressure and nanocatalyst have been experimentally examined for the yield (85%) of the product. The structural analysis of exo-THDCPD is carried out by 1H NMR and FTIR techniques and the physicochemical properties have also been evaluated. Good quality nanocatalyst Ni/MCM-41 has been synthesized by impregnation incipient wetness method and characterized by XRD, EDAX, TEM, and BET techniques. The nanocatalyst is highly reactive due to its mesoporous structure having appropriate size and shape which gives free diffusion of the molecules. Repeatability of the nanocatalyst shows good reactivity up to the four runs.

New insights towards strikingly improved room temperature ethanol sensing properties of p-type Ce-doped SnO2 sensors.

In this article, room temperature ethanol sensing behavior of p-type Ce doped SnO2 nanostructures are investigated successfully. Interestingly, it is examined that the abnormal n to p-type transition behavior is caused by Ce doping in SnO2 lattice. In p-type Ce doped SnO2, Ce ion substituting the Sn is in favor of generating excess holes as oxygen vacancies, which is associated with the improved sensing performance. Although, p-type SnO2 is one of the important materials for practical applications, it is less studied as compared to n-type SnO2. Pure and Ce doped SnO2 nanostructures were successfully synthesized by chemical co-precipitation method. The structure, surface morphology, unpaired electrons (such as free radicals), and chemical composition of obtained nanoparticles were studied by various kinds of characterization techniques. The 9% Ce doped SnO2 sensors exhibit maximum sensor response of ~382 for 400 ppm of ethanol exposure with fast response time of ~5 to 25 sec respectively. Moreover, it is quite interesting that such enhancement of ethanol sensing is unveiled at room temperature, which plays a key role in the quest for better ethanol sensors. These remarkably improved sensing results are attributed to uniformly distributed nanoparticles, lattice strain, complex defect chemistry and presence of large number of unpaired electrons on the surface.

Ferromagnetic resonance of NiCoFe2O4 nanoparticles and microwave absorption properties of flexible NiCoFe2O4-carbon black/poly(vinyl alcohol) composites.

The effect of cationic disorder and particle morphology on the ferromagnetic resonance (FMR) of NiCoFe2O4 nanoparticles (NPs) and the electromagnetic shielding effectiveness of flexible composites (wherein the nanoparticles are used as fillers) has been presented. Upon annealing at 1000 °C, spherical, ∼25 nm, single crystalline (as-prepared) NPs are transformed into octahedral, ∼200 nm, polycrystalline (annealed) NPs and change the cationic distribution significantly. The effect of shape, size and cationic distribution on the resonance properties has been discussed using the randomly-oriented anisotropic-axis model. The temperature dependent evolution of FMR spectra has been found to be consistent with a Bloch spin-relaxation model. Analysis of the FMR spectra reveals that NiCoFe2O4 nanoparticles have a large internal magnetic field along with broad FMR linewidths of ∼2-3 kOe, signifying high magnetic losses that are essential for the absorption of electromagnetic (EM) waves. Next, NiCoFe2O4-carbon black (NCF-CB) hybrids grafted in a PVA matrix, as flexible composite films with a thickness of ∼1.5 mm, are assessed for EM wave absorption properties in the range of 8-18 GHz. As compared to annealed-NCF-CB/PVA (21 dB, ∼99.5%), the as-prepared-NCF-CB/PVA composite film exhibits significantly large SE of 27 dB (∼99.9% attenuation of the EM wave), with a dominant contribution from absorption (SEA ∼ 21 dB). The electrical conductivity, the electric modulus, and Cole-Cole plots reveal that the dielectric losses in the as-prepared-NCF-CB/PVA have significant contributions from cationic disorder and particle size, as compared to the annealed-NCF-CB/PVA composites. Cationic disorder increases the d-d electron transition probability between adjacent ionic pairs such as Co2+/Fe3+ and a reduced particle size creates large interfacial polarization in the as-prepared NCF/CB hybrids. Considerably large values of the Landes g-factor, magnetic anisotropy and better impedance matching indicate a dominant magnetic loss contribution in ap-NCF (g = 4.5) as compared to an-NCF (g = 2.5) at 300 K.

Observation of magnetic anomalies in one-step solvothermally synthesized nickel-cobalt ferrite nanoparticles.

Magnetic anomalies corresponding to the Verwey transition and reorientation of anisotropic vacancies are observed at 151 K and 306 K, respectively, in NiCoFe2O4 nanoparticles (NPs) synthesized by a modified-solvothermal method followed by annealing. Cationic disorder and spherical shape induced non-stoichiometry suppress the Verwey transition in the as-synthesized NPs. On the other hand, reorientation of anisotropic vacancies is quite robust. XRD and electron microscopy investigations confirm a single phase spinel structure and the surface morphology of the as-synthesized NPs changes from spherical to octahedral upon annealing. Rietveld analysis reveals that the Ni(2+) ions migrate from tetrahedral (A) to octahedral (B) sites upon annealing. The Mössbauer results show canted spins in both the NPs and the strength of superexchange is stronger in Co-O-Fe than Ni-O-Fe. Magnetic force images show that the as-synthesised NPs are single-domain whereas the annealed NPs are multi-domain octahedral particles. The FMR study reveals that both the NPs have a broad FMR line-width; and resonance properties are consistent with the random anisotropy model. The broad inhomogeneous FMR line-width, observation of the Verwey transition, tuning of the magnetic domain structure as well as the magnetic properties suggest that the NiCoFe2O4 ferrite NPs may be promising for future generation spintronics, magneto-electronics, and ultra-high-density recording media as well as for radar absorbing applications.

Influence of texture coefficient on surface morphology and sensing properties of W-doped nanocrystalline tin oxide thin films.

For the first time, a new facile approach based on simple and inexpensive chemical spray pyrolysis (CSP) technique is used to deposit Tungsten (W) doped nanocrystalline SnO2 thin films. The textural, optical, structural and sensing properties are investigated by GAXRD, UV spectroscopy, FESEM, AFM, and home-built sensing setup. The gas sensing results indicate that, as compared to pure SnO2, 1 wt % W-doping improves sensitivity along with better response (<2 s) and recovery time (<25 s) toward NO2 gas at operating temperatures of ∼225 °C. The optimal composition of 1 wt % W-doped films exhibit lowest crystallite size of the order of ∼8-10 nm with reduced energy band gap and large roughness values of 3.82 eV and 3.01 nm, respectively. Reduction in texture coefficient along highly dense (110) planes with concomitant increase along loosely packed (200) planes is found to have prominent effect on gas sensing properties of W-doped films.